1. Field of the Invention
This invention relates generally to spatial light modulators and, more particularly, to a spatial light modulator with radially oriented active light modulating sectors for radial and angular analysis of beams of light, including Fourier transform optic patterns, for uses such as characterizing, searching, matching or identifying shape content of images.
2. State of the Prior Art
There are situations in which useful information can be derived from spatially dispersed portions of light beams. In particular, when an image is being carried or propagated by a light beam, it may be useful to gather and use or analyze information from a particular portion of the image, such as from a particular portion of a cross-section of a beam that is carrying an image.
For example, in my co-pending U.S. patent application, Ser. No. 09/536,426, which is incorporated herein by reference, narrow, radially oriented portions of a Fourier transform of an image are captured and detected in the spatial domain and used to characterize and encode images by shape for storage, searching, and retrieval. As explained therein, such radially oriented, angularly or rationally spaced portions of light energy from a Fourier transform, i.e., Fourier domain, of an image are captured sequentially in the spatial domain by positioning a rotating, opaque mask or wheel with a radially oriented slit in the Fourier transform domain of a light beam carrying the image after passing the light beam through a Fourier transform lens and detecting the light in the spatial domain that passes through the slit at various angular orientations, i.e., degrees of rotation. The light energy detected in the spatial domain that is passed through the slit in the Fourier domain at each angular orientation is characteristic of the portions of the image content that are generally linearly aligned in the same angular orientation as the slit in the rotating mask when the light energy is detected.
That system with the rotating, radially oriented, slit does perform the task of characterizing and encoding images by shape content of the images quite well and quite efficiently. However, it still has several shortcomings. For example, resolution of spatial frequency of an image at each angular orientation of the rotating slit is not as good as some applications or uses of such a system might require. Also, the spinning mask or wheel with an associated drive mechanism, like all mechanical devices, has stability and long term reliability issues, not to mention size and weight requirements.